Abstract

STUDY OF HYDROGEN CYANIDE PRODUCTION AS A MECHANISM OF ANTIFUNGAL ACTIVITY OF FLUORESCENT PSEUDOMONAS SPECIES AGAINST PHYTOPATHOGENIC PYTHIUM AND FUSARIUM SPECIES

*Balkrishna M. Sandikar

Abstract

Among 150 Pseudomonas isolates obtained from rhizosphere of healthy crop plants, nine isolates showed good in vitro antagonistic activity against phytopathogenic Pythium and Fusarium species. These Pseudomonas isolates were tested for ability to produce HCN by inverted plate technique on nutrient sucrose agar (NSA) supplemented with glycine and FeCl3, in Petri plates with picric acid discs fixed inside the lid. Among the nine Pseudomonas isolates, three were found to produce hydrogen cyanide as a metabolic product. Study of morphological, cultural, biochemical and genetic characters identified these isolates as Pseudomonas aeruginosa 13, P. aeruginosa58, and P. fluorescens 106. A direct correlation between the extent of HCN production and fungal growth inhibition was observed. These three HCN producing Pseudomonas isolates also showed other mechanisms of antifungal activity such as production of antibiotics and siderophores. Other six isolates which did not produce HCN showed good antifungal activity. This indicated that, HCN production is one of the important mechanisms of antifungal activity by Pseudomonas species but not always involved in inhibition or killing of phytopathogenic fungi. These Pseudomonas isolates were also found more effective to control fungal Infections of crop plants, in pot culture experiments.

Keywords: Pseudomonas, Phytopathogenic fungi, Antifungal activity, Hydrogen cyanide.